|Product Model:||Direct-Current Resistance Electric Bridge ZC-7 Electrical Tools||Weight:||Approximately 6kg|
500mA Digital Earth Resistance Tester,
6F22 Digital Earth Resistance Tester,
1.1A electrical earth tester
Direct-Current Resistance Electric Bridge ZC-57 Electrical Tools
ZC57 Direct-Current Resistance Electric Bridge
Instructions for Use
Applications & Features
ZC7 is a portable and precise direct-current double bridge, applying Kelvin circuit. The range of measurement is from 0.01μΩ to 1.1111 KΩ, which is divided into 7 capacities. It is internally equipped with a null indicator and can be equipped with enclosed working batteries, thus it can be used for measurement without any other accessories except for conducting wires. It is applicable for the laboratories, workshops and field work sites of the industrial and mining firms and scientific research organizations to precisely measure various low direct-current resistances, such as conductivity of metallic conductors, resistance of direct-current diverter, contact resistance of switch, cable resistance and direct-current resistances of various electrical machines and transformer windings.
The main resistance elements of the electric bridge are made of manganin wire with low humidity coefficient, and go through strict processing and long-term manual treatment. The switch is a precise change-over switch, with extremely low contact resistance as well as contact resistance variation. The null indicator adopts JZ2A modulation-type amplifier, with the advantages of high sensitivity, low noise and energy-saving.
The electric bridge is also equipped with external power and external null indicator wiring terminals, suitable for various users in different occasions.
This electric bridge is characterized by small size, portability, easy use, high accuracy, wide measuring range, high stability and high feasibility.
Primary technical indexes
All the technical indexes of ZC57are in conformity with the requirements of the national standards GB3930-83 <Direct-Current Electric Bridge for the Use of Resistance Measurement>, the professional standards ZBY164-83<Direct-Current Electric Bridge for the Use of Resistance Measurement>, and the international standards IEC564-77 < Direct-Current Electric Bridge >.
Primary parameters: shown in Table 1:
|Multiplying Factor||Effective Range||Resolving Power||Class of Accuracy (C)||Reference Resistance (RN)||Test Current|
Limit of intrinsic error
Elim = ±C%(RN/10+X)
Elim: limit of intrinsic error; RN: reference value; C: class of accuracy; X: reading of measuring dial.
Environmental conditions for use:
Reference value: temperature 20±0.5ºC; relative humidity 40%-60%
Nominal value: temperature 20±5ºC; relative humidity 25%-75%
The enclosed null indicator has the mechanical and electric zero-adjustment device, and the sensitivity is adjustable.
The damping time is no more than 4 seconds.
Sensitivity: for the electric bridge starting from the balance point, when the resistance value deviates from a class index value, the hand of the null indicator should deflect more than 1 grid.
Noise: the tremble of the hand should be no more than 1/3 grid.
There is a socket for the external null indicator installed in the battery box at the back of the electric bridge.
Power: the working power for the electric bridge is R40 1.5V dry batteries with parallel connection; the power for the enclosed null indicator is a 6F22 9V dry battery.
Weight: approximately 6kg
Basic working principle
The principle circuit of ZC57 is shown in Figure 1. The electric bridge is made up of 4 parts, including multiplying factor arm, measuring dial, null indicator and power circuit. And the multiplying factor arm is made up of 7 symmetry pairs of resistors, among which the ones in the bridge circuit are fixed standard resistor Rs, and the ones in the power circuit are current-limiting resistors. The measuring dial is made up of 5 stepping dials, which belongs to the typical Kelvin circuit.
Put 2 Size D dry batteries and a 6F22 9V integrated battery in the battery box at the back of the electric bridge based on the polarity. Turn the multiplying factor switch from the "disconnection" position to the "BV" and "GV" positions. Power voltage check: the hand of the null indicator should enter the green line area, showing that the working batteries of the bridge and the battery voltage of the null indicator are normal. Preheat for 5 minutes, and then adjust the "zero-adjustment" knob, making the hand point at "0". Turn the multiplying factor dial and the measuring dial for several times, ensuring that the contact between the switch and the dial is good.
Connect the resistor to be measured to the wiring terminals C1, P1, P2 and C2 of the electric bridge according to the 4-terminal method, as shown in Figure 2, in which the one between A and B is the resistor to be measured. When measuring the resistance lower than 0.1Ω, the resistance of the connecting wire for the measurement use should be no more than 0.01Ω.
Estimate the resistance value, and choose the appropriate multiplying factor and measuring dial. Press Button "G" and "B", at the same time adjust the measuring dial, making the null indicator point at zero again, the electric bridge is balanced at this time, and the resistance Rx is:
Rx = multiplying factor × reading of the measuring dial
At the beginning, the sensitivity of the null indicator should be lower, then increase after the electric bridge obtains the initial balance, in this way the measuring time can be shortened and the damage of the hand of the null indicator can be avoided.
Measuring dial: in order to ensure that the measuring value has enough significant digits, choose appropriate multiplying factor. Make the reading of the first measuring dial (on the farthest left) not equal to zero to ensure that the accuracy of the measuring value has enough resolving power. The dot at the bottom left of the first measuring dial is the decimal point. The "X" of each measuring dial represents 10.
External power and external null indicator
When you need to continuously measure low-value resistors for a long time, we recommend you to use external power for power supply. Turn the power optional switch to "B external", and connect the external power to the "B external" wiring terminals based on the polarity. If the enclosed null indicator is not sensitive enough during measurement, high-sensitivity external null indicator can be connected from "G external" wiring terminals, and at the same time turn the optional switch to "G external".
When measuring the resistance lower than 0.1Ω, the Button "B" should be used intermittently for saving energy. When measuring the direct-current resistance with inductance, Button "B" should be pressed prior to Button "G"; when releasing the buttons, Button "G" should be released prior to Button "B".
When measuring the direct-current resistance of large and medium-sized transformer coil, the 4 measuring conducting wires should be intertwisted with the purpose of improving the anti-interference ability against the electromagnetic field and earth's magnetic field. In order to further improve the anti-interference ability, the grounding wiring terminal should be connected with the earthing cable.
When the usage of the electric bridge is completed, reset the Button "B" and "G", and put the multiplying factor switch in the "disconnection" position. If the electric bridge won't be used for a long time, take all the batteries out.
The environmental conditions for the electric bridge storage: temperature 5-35°C; relative humidity 25%-80%; no corrosive gas in the air; keep out the direct rays of the sun.
Under the circumstance that the user obeys the requirements for use, delivery and storage specified in the technical requirements, within a year from the delivery and verification day, for the damage or failure of the product caused by inferior product quality, the manufacturer will repair the product for free, and if the product can't be repaired, the manufacturer will replace the damaged parts for free or even replace the product.
Certificate of compliance
Instructions for use
Contact Person: Rocky